I have a Tapco 4400 dual reverb, solid state, unit that is not working. I replaced the fuse, and the power is there, input signal goes through and the controls for in/out level work. The meter works, the mute works, but the reverb and eq do not. I've looked extensively at the board and do not see any burned places.

In any reverb failure, well any failure at all for that matter, isolate the problem. No reverb will either be the reverb pan, the cabling, or the support circuitry.

Disconnect the reverb pan and measure for continuity through its transducer coils - either end open?

With the thing running and reverb controls up, take the cables that went to the pan and touch the tip of each plug. One of them should make hum, and that is the return, and plugs into the OUTPUT jack on the pan. If that doesn't happen, then no reverb would happen.

With test signal applied to a channel input, scope the other cable - the drive cable - is there signal appearing there that woul;d drive the reverb pan?

I found out it's in the reverb pans. One of them was barely connect inside and that one works now. On the other, one of the coils has a short even though the wires and the unit look new. I was able to get it to work by moving it around and siliconed glued the wire to the brace to hold it in place and that seems fine.